1. Field of the Invention
The present invention relates in general to antenna structures, and in particular to an external antenna structure that can be detached from a wireless communication device.
2. Description of the Prior Art
External antennas are used to wireless communication devices to receive and transmit radio signals for increased efficiency in the communication. Most antennas are generally fixed to the housing of a wireless communication device without movement. These fixed antennas have a limited receiving and transmitting degree of the radio signals and suffer from the risk of being broken or damaged during the life of the wireless communication device. Fixing or replacing the permanent antenna's connection often requires a costly repair and removal of the wireless communication device from service for a period of time.
U.S. Pat. No. 6,518,928 discloses a conventional antenna device having a rotation limited structure. The antenna device includes a housing secured to an electric facility, a seat rotatably received in the housing, and an antenna element rotatably secured to the seat with a pivot pin. The housing includes a curved recess formed in the upper portion. The seat includes a projection protruding radially and slidably engaged in the curved recess of the housing, for limiting the projection to slide along the curved recess of the housing and for limiting the rotational movement of the seat relative to the housing and for preventing electric wires from being twisted. However, the antenna device is secured to a fixed place of the electric facility without movement, which is difficult to adjust a suitable receiving and transmitting direction/location and disassemble the antenna from the electric facility.
Hence, an improved antenna is desired to overcome the above-mentioned disadvantages of the prior art.